Background levels of238U and226Ra in atmospheric aerosols

The²³⁸U and²²⁶Ra contents of small-volume aerosols are determined by a chemical analysis technique. Mean activity concentrations of²³⁸U and²²⁶Ra in aerosols over approximately ten years are 0.29·10^–5 and 0.93·10^–5 Bq/m³, respectively. The yearly variation of²³⁸U and²²⁶Ra in aerosols is small. The concentrations of²²⁶Ra are always larger than those of²³⁸U in the same sampling time. The correlation of²³⁸U and²²⁶Ra cannot be recogonized (r=0.18). The concentrations of summer samples are greater than those of winter samples for²³⁸U. One of the causes of seasonal difference may be due to the fact that the components of aerosols are different according to soil size, soil components, weathering states, etc.     

Activity concentrations of238U and226Ra in agricultural samples

Distributions of²³⁸U and²²⁶Ra in agricultural samples and cultivated soils have been studied over ten years. The crops are rice, spinach and Chinese cabbage. Two investigated areas have been selected (35° 18 N, 113° 35 E). The agricultural samples and soils were collected annually from May 1982 through October 1991. The activity concentrations of²²⁶Ra in agricultural samples are greater than those of²³⁸U. The transfer factors of²³⁸U,²²⁶Ra are from 0.06·10^–3 to 1.2·10^–3. The²²⁶Ra/²³⁸U ratios for three agricultural samples have their characteristic values.     

Measurement of the radioactivity of238U,232Th,226Ra,137Cs and40K in soil using direct Ge(Li) γ-ray spectrometry

Radioactivity of the nuclides²³⁸U(²³⁵U),²³²Th,²²⁶Ra,¹³⁷Cs and⁴⁰K was measured in soil by direct -ray spectrometry using Ge(Li) detector. Relative laboratory method was used. Soil was dired, powdered, sieved and put into hemetically sealed container. CCRMP certified reference materials and compounds of the above nuclides mixed with fine quartz sand were used as references. Five and four -lines were used for the determination of²³²Th and²²⁶Ra, respectively, to obtain more accurate results. The most significant interferences, caused by the limited energy resolution of the detector, were resolved. In the case of ordinary soils, using one day duration of measurement and 1 kg mass of soil,²³²Th,²²⁶Ra and⁴⁰K can be determined with less than 10% relative random error. Elevated concentrations of²³⁸U(²³⁵U) and²²⁶Ra were observed in soil samples collected around a coal-fired power plant in Ajka town, Hungary.     

Radium,uranium and thorium concentrations in low specific activity scales and in waters of some oil and gas production plants

Low specific activity scales consisting of alkaline earth metal carbonates and sulfates are often present in some gaseous and liquid hydrocarbon plants; these scales contain a certain concentration of radium, uranium and thorium, which can cause a risk of -irradiation and of internal radiocontamination when they must be mechanically removed. That being stated,²³⁸U,²³²Th and²²⁶Ra were determined in scales, sludges and waters coming from different plants.²³⁸U and²³²Th concentrations were found very low; the isotopes²³⁸U and²³⁴U resulted in radioactive equilibrium, whilst²³²Th and²²⁸Th were not always in equilibrium.²²⁶Ra concentration was higher in scales and sludges than in waters.     

Alpha-emitting radionuclide contents in food samples as related to the Chernobyl accident

As a preliminary survey to establish intake of -emitting nuclides, in particular^239,240Pu, from a daily diet for inhabitants living near the Chernobyl reactor site, some kinds of food samples including total diet samples were collected in the Chernobyl (Ukraine) area and in the Ibaraki prefecture (Japan). Plutonium-239 and 240 were determined together with naturally occurring -emitters²²⁶Ra and U isotopes (²³⁴U,²³⁵U and²³⁸U) by -spectrometry after chemical separation. In most of the samples studied,^239,240Pu was less than the detectable amount, but in some mushrooms from the Ukraine it was found to be 41.6 mBq kg^–1 (wet mass) with a high activity ratio(0.58±0.08) of²³⁸Pu/^239,240Pu, indicating that nearly 100% of the^239,240Pu was attributable to the accident. Concentrations of²²⁶Ra and²³⁸U varied largely, depending on the samples. The measured activity ratios of²³⁵U/²³⁸U for some samples showed the isotopic composition of natural uranium.     

The dietary intake of238U,234U,230Th,232Th,228Th and226Ra from food and drinking water by inhabitants of the Walbrzych region

Intake with food and water of the natural radionuclides of the uranium and thorium series was determined for adult population of the south-western region in Poland, where in the 1950-ies an exploration of uranium ore was conducted. Concentration of the radionuclides was determined in food products and drinking water and their annual intake was estimated on the basis of the average annual consumption. The intake of²³⁸U,²³⁴U and²³⁰Th occurred mainly with water (33% to 68%), whereas the intake of²³²Th,²²⁸Th and²²⁶Ra was mainly with vegetables, potatoes, milk and flour. From the intake and dose coefficients the annual effective doses from the ingested radionuclides were calculated. The total dose was 5.6 Sv, of which 74% originated from²²⁶Ra.     

Radioactive contamination of the environment as a result of uranium production: a case study at the abandoned Lincang uranium mine,Yunnan Province,China

The distribution of radioactive pollutants, such as²²²Rn, U, Th and²²⁶Ra in the air, surface waters, soils and crops around the Lincang uranium mine, Yunnan Province, China, is studied. The mechanical, geochemical and biogeochemical processes responsible for the transport and fate of the radioactive elements are discussed based on the monitoring data. The pollutants concentrations of effluents from the mine tunnels were dependent on pH and which were controlled by biochemical oxidation of sulfide in the ore/host rocks. Radon anomalies in air reached 4 km from the tailings pile depending on radon release from the site, topography and climate.²³⁸U and²²⁶Ra abnormities in stream sediments and soil were 40—90 cm deep and 790—800 m away downstream. Anomalies of radioactive contaminants of surface watercourses extended 7.5—13 km from the discharge of effluents of the site mainly depending on mechanical and chemical processes. There were about 2.86 ha rice fields and 1.59 km stream sediments contaminated. Erosion of tailings and mining debris with little or no containment or control accelerated the contamination processes.

     

Radioactive contamination of the environment as a result of uranium production: a case study at the abandoned Lincang uranium mine,Yunnan Province,China

The distribution of radioactive pollutants, such as²²²Rn, U, Th and²²⁶Ra in the air, surface waters, soils and crops around the Lincang uranium mine, Yunnan Province, China, is studied. The mechanical, geochemical and biogeochemical processes responsible for the transport and fate of the radioactive elements are discussed based on the monitoring data. The pollutants concentrations of effluents from the mine tunnels were dependent on pH and which were controlled by biochemical oxidation of sulfide in the ore/host rocks. Radon anomalies in air reached 4 km from the tailings pile depending on radon release from the site, topography and climate.²³⁸U and²²⁶Ra abnormities in stream sediments and soil were 40—90 cm deep and 790—800 m away downstream. Anomalies of radioactive contaminants of surface watercourses extended 7.5—13 km from the discharge of effluents of the site mainly depending on mechanical and chemical processes. There were about 2.86 ha rice fields and 1.59 km stream sediments contaminated. Erosion of tailings and mining debris with little or no containment or control accelerated the contamination processes.     

Determination of226Ra and uranium in fish samples from waters of the Grand Canyon by alpha spectroscopy without electrodeposition

A previous paper reported the application of a method for determining²²⁶Ra by -spectroscopy. This paper presents important improvements which permit the determination of²²⁶Ra in the presence of large amounts of Ca. The method was applied to the analysis of²²⁶Ra and U isotopes in fish samples from the waters of the Grand Canyon.²²⁶Ra ranged from 0.05 Bq kg^–1 /1.4 pCi kg^–1/ to 0.17 Bq k^–1 /4.7 pCi kg^–1/.²³⁸U values ranged from 0.13 Bq kg^–1 /3.5 pCi kg^–1/ to 0.52 Bq kg^–1 /14 pCi kg^–1/ and²³⁴U values were between 0.23 Bq kg^–1 /6.2 pCi kg^–1/ and 12 Bq kg^–1/ /326. pCi kg^–1/.     

Correlated concentration distributions of natural alpha-radionuclides in sediment samples along the Romanian sector of the Danube river and the Black Sea coast

The concentrations of²³⁸U and²³²Th were determined by neutron activation analysis using epithermal irradiation in 12 sediment samples, collected along the Romanian sector of the Danube river and the Black Sea coast during 1994. The concentrations of²²⁶Ra were determined by the emanation method in the same sediment samples. The concentration ranges obtained were compared also with the²¹⁰Po concentration range for the same sector, reported in a previous paper. The accumulation potential of -emitting radionuclides in the analysed sediments is discussed.     

Correlation of natural and artificial radionuclides in soils with pedological,climatological and geographic parameters

Various types of soil samples were collected in the southern part of Brazil, with depth intervals of 5 cm, down to 50 cm, using a specially designed sampler. Pedological analysis of these soils were performed. Nuclear activities of¹³⁷Cs (expressed in Bq m^–2) and radioactive natural element (²²⁶Ra,²²⁸Ra and⁴⁰K) concentrations were determined by low background gamma-ray spectrometry.¹³⁷Cs concentrations were correlated with radioactive natural element concentrations and pedological, climatological and geographic parameters related to the soil samples collected.     

Influence of geology and soil particle size on the surface-area/volume activity ratio for natural radionuclides

The radioactive concentrations of²²⁶Ra,²³²Th,²³⁵U and⁴⁰K in surface soil of the province of Cáceres (Spain) were studied as a function of the geology and grain size. The activities of the four radionuclides in granitic and metamorphic soils have normal frequency distributions, with the mean value being significantly higher for the granitic soils than for the metamorphic soils. Sedimentary soils present asymmetric distributions, and their activities lie between the previous two types. The specific activities of the four radionuclides rises as the particle radius decreases. The equationA _e =(P ₁/R)+P ₂ describes the dependence of the specific activityA _e on radiusR, P ₁ andP ₂ being parameters that are related to the surface area and volume activities of the grains. The isotopes²²⁶Ra,²³²Th and²³⁵U accumulate with greater intensity on the surface of the grains than⁴⁰K. This effect is more pronounced in granitic and sedimentary soils than in metamorphic soils.     

Natural radionuclides and cesium-137 content in Arabian Gulf bottom sediments

The activity concentration of natural radionuclides and¹³⁷Cs in the bottom sediment samples from the coastal area of Kuwait on the Arabian Gulf have been determined by -ray spectrometry with REGe detector. The data for the samples are very similar to those obtained for surface soil samples in Kuwait.¹ Two parent-progeny ratios for:^23$Th–²²⁶Ra and²²⁸Ac–²⁰⁸Tl to evaluate the geochemical behavior of the radionuclides have been estimated. The existence of a serious disequilibrium between²³⁴Th and²²⁶Ra for samples taken from the vicinity of Kuwait islands and the Ras Al-Zoor area was found. The strait between the coast of Kuwait and Bubiyan island is proposed for the future sedimentation rate determinations on the basis of²¹⁰Pb measurements. No serious contamination by technogenic radionuclides for this region of Arabian Gulf was observed.     

Determination of radionuclides in the environment using gamma-spectrometry

Summary Seventy nine samples, including soil and rock, were collected from the agrestic region of the State of Pernambuco, Brazil. The activity concentrations of ²³⁸U and ²²⁶Ra in the samples were determined by gamma-spectrometry using an HPGe detector. The concentrations of ²³⁸U were 22 Bq ^. kg^-1 to 22 kBq ^. kg^-1. The concentrations of ²²⁶Ra were 14 Bq ^. kg^-1 to 17 kBq ^. kg^-1. The ²³⁸U/²²⁶Ra ratios in the soil were 0.7 to 3.4 (arithmetic mean 1.7). The radiometric data were evaluated to explain ²³⁸U and ²²⁶Ra migration in the soil and the possible consequences to the environment.     

Using the 186-keV peak for 226Ra activity concentration determination in Hungarian coal-slag samples by gamma-ray spectroscopy

The uranium isotopic abundance and the ²³⁸U–²²⁶Ra secular equilibrium were determined in nine Hungarian coal slag samples. The ²²⁶Ra activity concentration was measured based on the radon decay products and also the ²²⁶Ra peak at 186 keV. Secular equilibrium existed in eight samples, whereas one sample showed a slight disequilibrium. The direct and fast measurement using only the 186 keV peak was validated which can be used after measuring the uranium isotopic ratio and verifying the ²³⁸U–²²⁶Ra secular equilibrium. This method can be used to measure the ²²⁶Ra content of high number of samples from the same geochemical background.     

Natural radiactivity of fresh waters in Serbia

Statistical tests were performed on the -spectrometry measurement data obtained during the last decade for the natural radionuclides⁴⁰K,²²⁶Ra and²³²Th, in water samples collected from the Danube River, the Sava River and its tributaries, ground waters and artificial lakes. The lognormal radiopotassium distribution indicates a single statistical population. The presence of break points in the frequency distribution plots indicates that data for²²⁶Ra and²³²Th do not come from a single statistical population. The annual iongestion of⁴⁰K,²²⁶Ra and²³²Th was calculated and expressed in Bq y^–1.     

Development of a sequential method for the determination of238U,234U,232Th,230Th,228Th,228Ra,226Ra,and210Pb. in environmental samples

A sequential analytical method for the determination of²³⁸U,²³⁴U,²³²Th,²³⁰Th,²²⁸Th,²²⁸Ra,²²⁶Ra and²¹⁰Pb in environmental samples was developed. Uranium and thorium isotopes are first chromatographically sepaaated using tri-n-octyl phosphine oxide (TOPO) supported on silica gel. The uranium isotopes are determined by alpha-spectrometry following extraction with TOPO onto a polymeric membrane. Thorium isotopes are co-precipitated with lanthanum fluoride before counting in an alpha spectrometer. Radium isotopes and²¹⁰Pb are separated by co-precipitation/precipitation with mixed barium/lead sulphate. Radium-226 is determined by gross alpha counting of the final BaSO₄ precipitate and²²⁸Ra by gross beta counting of the same source. Lead-210 is determined through beta counting of its daughter product²¹⁰Bi.     

Development of new centrifuges for fast solvent extraction of transactinide elements

Inductively coupled plasma-mass spectrometry (ICP-MS) was used to concurrently determine multiple long-lived (t_1/2>10⁴ y) actinide isotopes in soil leachates. Ultrasonic nebulization was found to maximize instrument sensitivity. Instrument detection limits for actinides in solution ranged from 50 mBq L^–1 (²³⁹Pu) to 2Bq L^–1 (²³⁵U). Hydride adducts of²³²Th and²³⁸U interfered with the determinations of²³³U and²³⁹Pu; thus, extraction chromatography was used to concentrate the analytes and separate uranium from the other actinides in advance of mass spectrometric determination. Alpha spectrometric determinations of²³⁰Th,²³⁹Pu, and the²³⁴U/²³⁸U activity ratio in soil leachates compared well with ICP-MS determinations; however, there were some small systematic differences (ca. 10%) between ICP-MS and -spectrometric determinations of²³⁴U and²³⁸U activities. These differences were attributed to the use of different isotope dilution spikes for ICP-MS and -spectrometry.     

Non-destructive determination of low-level210Pb and226Ra with an ordinary high-purity Ge-detector

A convenient non-destructive method for the determination of low level²¹⁰Pb and²²⁶Ra with an ordinary high-purity Ge-detector is presented. The ordinary Ge-detectors used in this work were available to measure 46.5 keV -rays of²¹⁰Pb. These detectors were also useful for the non-destructive analysis of low-level²²⁶Ra in lime-stone and calcium chemicals when a stream of nitrogen gas was maintained around the detectors. By this method, measurements could be carried out not only for²¹⁰Pb and²²⁶Ra but also for other -emitting radionuclides simultaneously, using the same detector. The detection limits of about 1 Bq per sample for²¹⁰Pb and about 0.05 Bq per sample for²²⁶Ra, respectively, were estimated, when the samples were counted for 1–2 days.     

Influence of Ba on the electrodeposition of226Ra

A detailed study of the influence of barium on the electrodeposition of²²⁶Ra was made using two different procedures. High yields (80–90%) were attained when the amounts of barium were not very significant. However, the²²⁶Ra yields fell drastically for amounts slightly greater than 0.10–0.15 mg of Ba, according to the electrodeposition procedure. Samples containing trace amounts of barium less than 100–150 g can thus be treated with no barium-radium separation being required.²¹⁰Po was also deposited, although practically no influence of barium on the Po plating was observed. The²²⁵Ra resolution rose uniformly (25 to 55 keV) as the amount of barium rose up to 1 mg. These resolutions allow one to make a direct accurate determination of²²⁶Ra as well as an indirect determination of²²⁴Ra and²²³Ra via measurement of their daughter products.